The present invention relates to an electric pump apparatus, particularly concerns such an electric pump apparatus made to be a compact for vehicle-mount, which has a reservoir for storing operating fluid, the reservoir has a constitution in which an electric motor serving as a driving source is integrally attached on one side of a pump via a bracket, a opening-side-end portion of a tank cylinder is secured on the pump-supporting surface of the bracket so as to surround the pump.
In recent years, automobiles are equipped with various hydraulic-actuating devices, such as a power steering apparatus and automatic transmission apparatus, which are actuated by oil pressure to assist driving operation. Accordingly, pumps which generates oil pressure for these hydraulic-actuating devices are also equipped.
This type of the pumps are generally driven by engine as a driving source; however, since engine widely changes its rotational speed while traveling, engine is not quite appropriate for the driving source. When engine is used as the driving source, various problems arise in which power-consumption for driving the pump causes an increase in fuel-consumption rate, and furthermore mounting position of the pump could be limited due to obtaining transmission from the engine. For these reasons, in recent years, electric pump apparatuses, which use an electric motor as a driving source that is driven by power supply from a car-mounted battery instead of the engine, have been replacing the engine-driven-pump apparatuses.
Meanwhile, electric vehicles (EVs) have been developed in order to prevent environmental deterioration due to exhaust gases, because the EV use an electric motor for the driving source instead of engine. Even the EVs may be mounted with hydraulic-actuating devices, therefore electric pump apparatuses using electric motors as driving sources are inevitably applied with respect to generation sources of oil pressure for such hydraulic-actuating devices.
Furthermore, with respect to the electric pump apparatuses of this type, compactness is strongly demanded in order to improve the mountability onto vehicles. Japanese Laid-Open Patent Application No. 10-82377 (1998) by the applicant of the present invention has disclosed an electric pump apparatus in which: a trump is supported on one side of a bracket with an electric motor being supported on the other side, and both of these are connected at the axial portion of the bracket while a bottomed-cylindrical tank cylinder being secured on the pump-supporting surface of the bracket so as to surround the pump, and thus a reservoir for storing operating fluid is constituted, furthermore, mountability onto vehicle is enhanced by integrating the reservoir and electric motor with the pump.
Here, in the above-mentioned electric pump apparatus disclosed in Japanese Laid-Open Patent Application No. 10-82377 (1998), securing of the tank cylinder is achieved by allowing a flange circumferentially provided on its opening-side-end portion to contact the supporting surface of the bracket and fastening them together with a supporting flange of the electric motor being contacted to the other surface of the bracket by a plurality of securing bolts placed along the circumferential direction. However, the problem with the electric pump apparatus is that the assembly including this securing process is very complex.
Here, in the case when the electric pump apparatus constructed as described above is mounted on a vehicle, so-called "longitudinally-aligned arrangement" in which a pump shaft (input shaft) of the pump is longitudinally connected with a motor shaft (output shaft) of the electric motor is mainly adopted. In some cases for types of vehicle having a limitation of their mounting position, so-called "transversally-aligned arrangement" in which the both shafts are transversally connected may be adopted.
In order to make it applicable to both types, two types of tank cylinders are prepared: one is for longitudinal application in which an oil filler port for operating fluid is opened on bottom surface that faces up when mounted, and the other is for transversal application in which similar oil filler port is opened on circumferential surface, and either of these types will be selected depending on the alignment type. However, if the assembly has been carried out with an incorrect selection, the tank cylinder can not be removed solely, and thus the assembly including the installation of the electric motor has to started over.
Moreover, the above-mentioned tank cylinder is made out of a thin cylindrical body, therefore it tends to be damaged due to various reasons while in-use. When a replacement of the tank cylinder is required due to such a damaged, a complex task including adjustments of assembly of the electric motor which needs to he removed together with the tank cylinder will also be required. Therefore, replacement on assembly basis including the pump and electric motor is conventionally conducted instead of on part basis; this causes an increase in costs required for the replacement.
Here, the pump in the electric pump apparatus constituted as described above is provided as a rotational volume type such as a gear pump or vane pump. In the pump of this type, since intermittent discharging are carried out in response to the rotation of rotors, it is not avoidable to have the discharging oil without containing pulsations. Therefore, this results in disadvantages such as damages in the piping system on discharging side and generation of noises.
These pulsations are generated mainly with a frequency corresponding to the product between rotational rate of the rotors and the number of discharges per rotation. For this reason, the pulsations are effectively reduced by placing an accumulator having its inner volume corresponding to this frequency in a halfway of the piping system on the discharging side.
However, in the car-mounted electric pump apparatus, it is difficult to mount the accumulator in the halfway of the piping system in the most of the cases. Therefore, in the aforementioned electric pump apparatus disclosed in Japanese Laid-Open Patent Application No. 10-82377 (1998), a suppression chamber having the aforementioned inner volume is constructed inside a reservoir formed on the other side of the pump, and this suppression chamber is used as an accumulator by communicating it with the discharging side of the pump, and thus pressure fluid whose pulsations have been reduced while passing through the suppression chamber is sent out to the discharging side.
As described above, the electric pump apparatus disclosed in Japanese Laid-Open Patent Application No. 10-82377 (1998) has a constitution in which the driving electric motor and reservoir are integrally formed with the pump. Moreover, the apparatus also has a constitution in which the pulsations on the discharging side is reduced by having the suppression chamber as an integral part; thus, it is very easy for car application.
However, the comparatively bulky suppression chamber that requires a predetermined inner volume as described above is placed together with the reservoir on the other side of the pump (on the opposite side to the mounting side of the electric motor), and the electric motor, pump, suppression chamber, and reservoir are aligned in the shaft direction. Therefore, this constitution limits a reduction of the entire size of the apparatus in the shaft direction, and thus it does not sufficiently meet the demand of compactness for car-mount-use.